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News Analysis A space probe that arrives at Venus today will yield new insights into what caused the runaway greenhouse effect there and could bring a salutary warning for our own planet, scientists say.

The European Space Agency's Venus Express will spend three years peering through a shroud of toxic sulfur clouds to glean information about the climate, atmosphere and curious 'backwards' rotation of the so-called pressure cooker planet.

It's also hoped the mission will help answer questions about what caused its mysterious 'resurfacing' some 500 million years ago and whether it is being shaken by seismic activity and volcanoes.

It may also provide clues about whether the Earth and Venus were once similar, and when and why they took such radically different paths, says Dr Frank Mills of the Australian National University, an expert in the chemistry of the Venusian atmosphere who has been working with scientists directly involved in the mission.

"There are many uncertainties in trying to reconstruct Venus' evolution," he says.

"Some of these may be resolvable by making appropriate observations."

The greenhouse effect

The UK's Royal Astronomical Society says "any astronaut unlucky enough to land [on Venus] would be simultaneously crushed, roasted, choked and dissolved".

Venus' atmosphere is 90 times denser than Earth's and 96% is made up of the greenhouse gas CO2.

Scientists say this causes a strong warming effect and heats the surface of the planet to around 500°C.

There are no signs of water on Venus and its surface is apparently more arid that the driest desert on Earth.